Cleaning parts is an important step in many applications, either for functional or aesthetic reasons. The cleaning process usually consists of contacting the part with a cleaner in such a manner that the soil is removed from the surface of the part and then the soil-containing cleaner is replaced with clean liquid. The part is then dried. Traditionally organic solvents have been used due to their effectiveness in removing many common contaminants in production processes, as well as their ability to be easily removed from the part due to their typically high volatility. Recently, tighter environmental regulations have led many users to abandon traditional organic solvent-based cleaners in favor of aqueous cleaner systems. The use of aqueous cleaner systems heightens drying problems, however.
There are many conventional drying processes currently being used to dry parts that have been cleaned using aqueous systems. Each of these methods has weaknesses that make them less than ideal for many commercial uses. Some of these traditional drying processes include vaporization through thermal and/or vacuum means, displacement with a suitable volatile solvent, alcohol rinsing, centrifugal spinning, evaporation at ambient temperature often promoted by using flowing air streams, air knife displacement, and manually wiping off the parts with a towel.
In general vaporization techniques suffer from spotting because the liquid is removed as a vapor, leaving any dissolved solids or low volatility liquids behind. Furthermore, thermal vaporization is slow and very energy intensive. Vacuum aided drying is also slow and requires relatively expensive equipment. Additionally, these vaporization techniques frequently impose additional constraints on parts handling following drying. In thermal systems the part may be to hot to handle immediately upon drying, causing delays or requiring special handling techniques. Furthermore, some parts may become deformed or discolored at higher temperatures, making thermal drying systems inappropriate. In vaporization techniques without added heat, the part will cool due to evaporative cooling which may cause condensation of moisture from the ambient air on the part. Evaporative drying is slower and suffers from the same spotting problems mentioned above. Materials used in fluorinated solvent displacement or alcohol adsorption systems are often costly, flammable or toxic, making them unsuitable for many uses. These materials may also be restricted in use due to their being volatile organic compounds and/or ozone depleting materials. Towel drying is labor intensive, slow and does not work well on intricate parts. For a general review of current drying techniques and their associated problems, see Charles S. Leech, Jr., "Rinsing and Drying Issues and Answers", Precision Cleaning, Jan 1994, pp. 13-17.
An ideal drying system would incorporate the best features of all of these methods without any of the drawbacks. In other words, it would be fast, it would use relatively little energy, it would be resistant to spotting and it would not require the use of solvents. It is an object of the present invention to provide such a method of drying.